Syndiotactic polystyrenie is a commercially important material useful in the preparation of articles and objects having an extremely high resistance to deformation due to the effects of temperature. The polymers have very high melting points and low solubility in organic solvents, due to a stereoregular structure, composed of phenyl groups alternating regularly from side to side of the chain.
Transition metal complexes have been used as Ziegler-Natta catalysts for the polymerization of olefins, including stereo specific polymerizations. For example, Group 4 half-sandwich complexes, such as titanocene, zirconocene or hafnocene derivatives, activated with methyl aluminoxane (MAO) are efficient homogeneous catalysts for the promotion of syndioselective polymerization of styrene. More recently, metal complexes of composition CpML.sub.2 +A--, where Cp is substituted or unsubstituted cyclopentadienyl, M is a transition metal, L is an anionic ligand, and A is a noncoordinating, compatible anion of a Bronsted acid salt, for example tetraphenyl borate, are have been used for syndiotactic polymerization of styrene. Formation of these metal-borate complexes requires an additional step in the polymerization process, however, and therefore increases production costs. A need exists for methylaluminoxane cocatalysts which do not require the preformation of the metal-borate complex, and which produce syndiotactic polystyrene in high yield.